Invested with underwear (4)
I believe the answer is:
vest
'underwear' is the definition.
'invested with' is the wordplay.
'with' indicates the answer is hidden within the clue.
'VEST' is hidden in the letters of 'invested'.
(Other definitions for vest that I've seen before include "American version of waistcoat" , "Upper undergarment, singlet" , "Sleeveless garment" , "An American man's waistcoat" , "Undergarment for vets" .)